In 36 years, Luis will be 3 times as old as he is right now. How old is he right now?
We can use the given information to write down an equation about Luis's age. Let Luis's age be $l$ In 36 years, he will be $l + 36$ years old. At that time, he will also be $3 l$ years old. Writing this information as an equation, we get: $l + 36 = 3 l$ Solving for $l$ , we get: $2 l = 36$ $l = 18$.